Electroacoustic transducer

Abstract

An electroacoustic transducer includes: a polygonal-shaped laminated piezoelectric element including alternately stacked piezoelectric layers and electrode layers, with the piezoelectric layers placed between at least one pair of electrode layers having different polarities; and a circular vibration plate on which the laminated piezoelectric element is placed. Of the piezoelectric layers sandwiched between the at least one pair of electrode layers, the total volume (V) of those effective layers that overlap the at least one pair of electrode layers as viewed from the stacking direction satisfies the condition below: 0.2π R 2 ×ts≤V ≤2.0π R 2 ×ts wherein π represents the ratio of the circumference of a circle to its diameter, R represents the radius of the vibration plate, and ts represents the thickness of the vibration plate.

What is claimed is: 
     
       1. An electroacoustic transducer, comprising:
 a laminated piezoelectric element comprising alternately stacked piezoelectric layers and electrode layers, with the piezoelectric layers placed between at least one pair of electrode layers having different polarities; and 
 a vibration plate on which the laminated piezoelectric element is placed; 
 said electroacoustic transducer is characterized in that: 
 the laminated piezoelectric element is polygonal in shape when viewed from a stacking direction; 
 the vibration plate on which the laminated piezoelectric element is placed is circular in shape and made of a metal; and 
 of the piezoelectric layers sandwiched between the at least one pair of electrode layers, a total volume (V) of effective layers that overlap the at least one pair of electrode layers as viewed from the stacking direction satisfies a condition below when V is approximated by a volume of the laminated piezoelectric element:
   0.2 πR   2   ×ts≤V≤ 2.0π R   2   ×ts  
 
 
 (wherein π represents a ratio of a circumference of a circle to its diameter, R represents a radius of the vibration plate, and ts represents a thickness of the vibration plate). 
 
     
     
       2. The electroacoustic transducer according to  claim 1 , characterized in that:
 the at least one pair of electrode layers include a first electrode layer and a second electrode layer having different polarities; 
 the first electrode layer is connected to a first side electrode formed on one side face of the laminated piezoelectric element; and 
 the second electrode layer is connected to a second side electrode formed on a side face different from the one on which the first side electrode is formed. 
 
     
     
       3. The electroacoustic transducer according to  claim 2 , characterized in that the first electrode layer includes an electrode layer formed on a surface of the laminated piezoelectric element on a side opposite the one that contacts the vibration plate. 
     
     
       4. The electroacoustic transducer according to  claim 1 , characterized in that the laminated piezoelectric element is square in shape when viewed from the stacking direction. 
     
     
       5. The electroacoustic transducer according to  claim 2 , characterized in that the laminated piezoelectric element is square in shape when viewed from the stacking direction. 
     
     
       6. The electroacoustic transducer according to  claim 3 , characterized in that the laminated piezoelectric element is square in shape when viewed from the stacking direction. 
     
     
       7. The electroacoustic transducer according to  claim 1 , wherein the vibration plate has a thickness of 0.05-0.5 mm. 
     
     
       8. The electroacoustic transducer according to  claim 2 , wherein the vibration plate has a thickness of 0.05-0.5 mm. 
     
     
       9. The electroacoustic transducer according to  claim 3 , wherein the vibration plate has a thickness of 0.05-0.5 mm.